Allow explicitly implemented ISimdVector APIs to be handled as intrinsic (#104983)

* Allow explicitly implemented ISimdVector APIs to be handled as intrinsic

* Apply formatting patch

Author: tannergooding

src/coreclr/jit/importercalls.cpp

@@ -10312,6 +10312,19 @@ NamedIntrinsic Compiler::lookupNamedIntrinsic(CORINFO_METHOD_HANDLE method)
                     else
                     {
 #ifdef FEATURE_HW_INTRINSICS
+                        if (strncmp(methodName,
+                                    "System.Runtime.Intrinsics.ISimdVector<System.Runtime.Intrinsics.Vector", 70) == 0)
+                        {
+                            // We want explicitly implemented ISimdVector<TSelf, T> APIs to still be expanded where
+                            // possible but, they all prefix the qualified name of the interface first, so we'll check
+                            // for that and skip the prefix before trying to resolve the method.
+
+                            if (strncmp(methodName + 70, "<T>,T>.", 7) == 0)
+                            {
+                                methodName += 77;
+                            }
+                        }
+
                         CORINFO_SIG_INFO sig;
                         info.compCompHnd->getMethodSig(method, &sig);
 
@@ -10530,6 +10543,25 @@ NamedIntrinsic Compiler::lookupNamedIntrinsic(CORINFO_METHOD_HANDLE method)
 #error Unsupported platform
 #endif
 
+                        if (strncmp(methodName,
+                                    "System.Runtime.Intrinsics.ISimdVector<System.Runtime.Intrinsics.Vector", 70) == 0)
+                        {
+                            // We want explicitly implemented ISimdVector<TSelf, T> APIs to still be expanded where
+                            // possible but, they all prefix the qualified name of the interface first, so we'll check
+                            // for that and skip the prefix before trying to resolve the method.
+
+                            if (strncmp(methodName + 70, "64<T>,T>.", 9) == 0)
+                            {
+                                methodName += 79;
+                            }
+                            else if ((strncmp(methodName + 70, "128<T>,T>.", 10) == 0) ||
+                                     (strncmp(methodName + 70, "256<T>,T>.", 10) == 0) ||
+                                     (strncmp(methodName + 70, "512<T>,T>.", 10) == 0))
+                            {
+                                methodName += 80;
+                            }
+                        }
+
                         if ((namespaceName[0] == '\0') || (strcmp(namespaceName, platformNamespaceName) == 0))
                         {
                             CORINFO_SIG_INFO sig;

src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs

@@ -4384,12 +4384,44 @@ private bool notifyInstructionSetUsage(InstructionSet instructionSet, bool suppo
                 // By policy we code review all changes into corelib, such that failing to use an instruction
                 // set is not a reason to not support usage of it. Except for functions which check if a given
                 // feature is supported or hardware accelerated.
-                if (!isMethodDefinedInCoreLib() ||
-                    MethodBeingCompiled.Name == "get_IsSupported" ||
-                    MethodBeingCompiled.Name == "get_IsHardwareAccelerated")
+                if (!isMethodDefinedInCoreLib())
                 {
                     _actualInstructionSetUnsupported.AddInstructionSet(instructionSet);
                 }
+                else
+                {
+                    ReadOnlySpan<char> methodName = MethodBeingCompiled.Name.AsSpan();
+
+                    if (methodName.StartsWith("System.Runtime.Intrinsics.ISimdVector<System.Runtime.Intrinsics.Vector"))
+                    {
+                        // We want explicitly implemented ISimdVector<TSelf, T> APIs to still be expanded where possible
+                        // but, they all prefix the qualified name of the interface first, so we'll check for that and
+                        // skip the prefix before trying to resolve the method.
+
+                        ReadOnlySpan<char> partialMethodName = methodName.Slice(70);
+
+                        if (partialMethodName.StartsWith("<T>,T>."))
+                        {
+                            methodName = partialMethodName.Slice(7);
+                        }
+                        else if (partialMethodName.StartsWith("64<T>,T>."))
+                        {
+                            methodName = partialMethodName.Slice(9);
+                        }
+                        else if (partialMethodName.StartsWith("128<T>,T>.") ||
+                                 partialMethodName.StartsWith("256<T>,T>.") ||
+                                 partialMethodName.StartsWith("512<T>,T>."))
+                        {
+                            methodName = partialMethodName.Slice(10);
+                        }
+                    }
+
+                    if (methodName.Equals("get_IsSupported", StringComparison.Ordinal) ||
+                        methodName.Equals("get_IsHardwareAccelerated", StringComparison.Ordinal))
+                    {
+                        _actualInstructionSetUnsupported.AddInstructionSet(instructionSet);
+                    }
+                }
             }
             return supportEnabled;
         }